If youth knew; if age could.

All that matters is love and work.

A string of reproaches against other people leads one to suspect the existence of a string of self-reproaches with the same content.

It often seems that the poet's derisive comment is not unjustified when he says of the philosopher: “With his nightcaps and the tatters of his dressing-gown he patches the gaps in the structure of the universe.

Cigars served me for precisely fifty years as protection and a weapon in the combat of life... I owe to the cigar a great intensification of my capacity to work and a facilitation of my self-control.

Like the physical, the psychical is not necessarily in reality what it appears to us to be.

The view is often defended that sciences should be built up on clear and sharply defined basal concepts. In actual fact no science, not even the most exact, begins with such definitions. The true beginning of scientific activity consists rather in describing phenomena and then in proceeding to group, classify and correlate them.